1. Field of the Invention
The present invention relates to armor systems. More particularly, the present invention relates to a first multi-layer armor system which can be a shroud for the containment of large, high velocity cutting projectiles, and to a second multi-layer armor system which is high velocity impact/ballistic resistant and minimizes deformation and penetrations from such an impact.
2. Prior Art
In the summer of 1989, a blade/blade fragment broke away from the turbine engine of an airborne aircraft and severed the aircraft's hydraulic system. The aircraft crash-landed soon after. Shrouds to contain flying blade fragments (projectiles) from a failed turbine engine to protect vital equipment in close proximity are known—these shrouds are formed from multiple layers of loosely woven aramid, such as Kevlar®, fabric. Similarly, shields to protect aircraft engines from damage by flying fragments from a source external to the engine are known; these can be soft armor shields formed from layers of woven aramid fabric, metal shields, or a combination of the two (see U.S. Pat. No. 4,057,359, hereby incorporated by reference).
In either event, with the number of woven fabric layers heretofore utilized, these prior art shrouds/shields are not as effective with respect to high velocity cutting impacts of a rapidly rotating engine blade which fractures and is hurled away from the higher power, larger engines of today. An obvious solution would be to increase the number of fabric layers. However, this solution suffers the same disadvantage of some of the metallic shields available, excessive weight and expense. Therefore, a lightweight armor system which could function as a projectile containing shroud is desirable. Such an armor system would have utility in many areas, i.e., wherever there is a potential for failure of equipment with high speed moving parts that could break into large fragments and become high velocity projectiles that cut and tear their way through adjacent parts/machinery.
Applicants have discovered such an armor system, and in the course of such discovery have also discovered a ballistic resistant armor system which minimizes armor deformation after a high velocity impact or ballistic impact. An armor system can stop an impacting object from completely penetrating the system and yet deform (or bulge) so badly on its non-impact side that damage occurs to the equipment or person being protected by the armor system.
Ballistic resistant articles such as vests, helmets, hard and soft armor, structural members of helicopters and other military equipment, vehicle panels, briefcases, raincoats and umbrellas containing high strength fibers are known. Fibers conventionally used in these articles include aramid fibers such as poly(p-phenylene terephthalamide), graphite fibers, nylon fibers, ceramic fibers, high strength polyethylene fibers, e.g., SPECTRA®, glass fibers and the like. For many applications, such as vests or parts of vests, the fibers are used in a woven or knitted fabric.
U.S. Pat. No. 4,623,574 discloses the formation of prepreg sheets comprised of elastomer coated high strength fibers which are substantially parallel and aligned along a common fiber direction. The patent teaches that the prepreg sheets can be plied together, with successive sheets being rotated relative to the first sheet, to form simple composite materials.
U.S. Pat. No. 4,181,768 teaches lightweight, rigid armor formed by press laminating alternating layers of 6,6 nylon film and aramid fabric. The fabric can be a nonwoven such as a needle punched felt.
U.S. Pat. No. 4,574,105 teaches a flexible, penetration resistant panel comprised of face plies of woven poly(p-phenylene terephthalamide) and backing plies of nonwoven polyamide, preferably needled polyamide felt. This patent teaches that the reverse configuration (face plies of polyamide felt backed with woven Kevlar fiber plies) decreases the ballistic limit velocity by 200 ft/sec. U.S. Pat. No. 4,608,717 teaches a flexible, protective armor comprising layers of aramid fiber fabric which sandwich a trauma attenuation layer of feathers, foam or felt. The layers are drawn together, preferably by stitching. There is no teaching of a felt comprising fiber with high tensile properties.
U.S. Pat. No. 4,623,574, commonly assigned, teaches a ballistic resistant composite comprising a network of high strength fibers which are substantially coated with an elastomeric matrix material. U.S. Pat. No. 4,737,401, also commonly assigned, teaches a ballistic resistant article which comprises at least one network of high strength extended chain polyethylene, polypropylene, polyvinyl alcohol or polyacrylonitrile fiber having a denier of not more than 500 and a tensile modulus of at least about 200 g/denier. In both of these patents, the network can be a felt.
U.S. Pat. No. 4,660,223 teaches body armor comprising an assemblage of panels, each panel consisting of an inner face ply of titanium metal bonded to a strike face ply of aramid fiber woven cloth. The assemblage of panels is held in a predetermined relationship by first and second layers of felt material, preferably of aramid fibers, which are bonded with adhesive plies to the inner and strike faces of the panels. The felt plies permit the panels to move relative to one another and thus avoid inhibiting body movement of the wearer.
U.S. Pat. No. 4,681,792, commonly assigned, teaches a flexible ballistic resistant article having first and second portions each comprising a plurality of fibrous layers where the resistance to displacement of fibers in layers where the resistance to displacement of fibers in each layer of the second portion is greater than that of each layer in the first portion. The layers of the first portion consist essentially of uncoated fibers comprising fiber selected from the group of polyolefin fibers, polyvinyl alcohol fibers and polyacrylonitrile fibers having a tensile modulus of at least 300 g/d and a tenacity of at least about 15 g/d, and the layers of the second portion consist essentially of uncoated fibers. According to the patent, woven fibrous layers exhibit a higher resistance to fiber displacement than nonwoven layers.
The present invention, was developed in an attempt to overcome the deficiencies of the prior art.